1. Field of the Invention
The present invention relates generally to construction equipment, and more particularly is a ladder mounted elevator device to raise loads.
2. Description of the Prior Art
People in the construction and building service industries are well aware of the many items that need to be raised to the roofs of various structures. The most common items to be lifted are of course the items that are installed on the roofs—roofing materials and heating, ventilating, and air conditioning equipment. These items are usually far to heavy to simply be carried up a ladder by a workman.
Various pieces of equipment have been utilized to resolve the elevating problem, among them cranes, cherry pickers, and helicopters. While these machines are certainly effective in raising the required loads, they are also expensive to operate, sometimes prohibitively so. Moreover, these machines require operating manpower in addition to that required for the actual installation at hand.
The prior art discloses many devices that have been proposed to address the problems of raising loads to a rooftop or to another elevated location. Various ladder hoists, hoist attachments, and ladder attachments to facilitate lifting have been offered for use in the painting, maintenance, HVAC, and construction trades.
Many such devices are essentially winches attached to a ladder, such as the “Lifting Device for Use with a Ladder” by Campbell, U.S. Pat. No. 5,911,287, issued Jun. 15, 1999. Another such device is the “Ladder Hoist Attachment” of Larson, U.S. Pat. No. 4,598,795, issued Jul. 8, 1986. Still another is the “Stabilized Ladder Power Winch System” of Pate, U.S. Pat. No. 5,139,108, issued Aug. 18, 1992. Still another is the “Extension Ladder Hoist” of Ziegelmann, U.S. Pat. No. 4,128,228, issued Dec. 5, 1978.
Other lifting devices incorporate a ladder or a ladder-like element with a hoist support arrangement to yield a portable hoist. One such device is the “Lift and Portable Lift” of Krotov, et al., U.S. Pat. No. 5,427,356. A similar device is the “Portable Hoist” of Killeen, U.S. Pat. No. 4,690,248, issued Sep. 1, 1987. A device that connects the hoist support to the terminal end of a ladder is the “Portable Swiveling Lift Device” of Sears, U.S. Pat. No. 5,738,185, issued Apr. 14, 1998.
The lack of widespread use of these prior art devices is attributable to their having one or more of the following shortcomings: (1) insufficient anchoring of the base of the ladder; (2) insufficient stabilization of the portion of the ladder from which the lifting force is applied; (3) lack of a safe and secure means of securing the upper end of the ladder; (4) the failure to provide sufficient power and mechanical advantage to lift large loads; (5) lack of easy portability; and (6) lack of compatibility with existing ladders.
Accordingly, it is an object of the present invention to provide a ladder elevator device that can be affixed to a standard ladder.
It is another object of the present invention to provide a device that has a stable base.
It is still another object of the present invention to provide a device that has adequate means of securing the lifting device to the roof top or other elevated area.
It is yet another object of the present invention to provide a device that is easily portable, but has adequate lifting power.
These and other objects and advantages of the present invention will become apparent to those skilled in the art in view of the description of the best presently known mode of carrying out the invention as described herein and as illustrated in the drawings.